DOC-13717 rest api for app telemetry

[ggray-cb]

This PR adds documentation for the Server /settings/appTelemetry REST API endpoint.

Here's a list of the changes in this PR, with links to a preview. You will need the Docs Team credentials on Confluence to access the preview.

• Added new Application Telemetry page that explains getting and configuring telemetry settings.
• Added a short section to Configure Prometheus to Collect Couchbase Metrics explaining that you can add application metrics to the Prometheus endpoint by enabling application telemetry. It seemed like the right place to mention that.

Note: I've made some assumptions about the maxScrapeClientsPerNode and scrapeIntervalSeconds settings, so be sure to pay special attention to their descriptions.

[Copilot]

Pull request overview

Adds Couchbase Server documentation for the /settings/appTelemetry REST API and cross-links it from Prometheus monitoring docs and navigation.

Changes:

• Adds a new REST API reference page for Application Telemetry (/settings/appTelemetry) with GET/POST examples and parameter descriptions.
• Updates Prometheus monitoring docs to mention enabling application telemetry to expose SDK/application metrics.
• Updates shared REST API curl parameter partial and adds the new page to the REST API navigation.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 8 comments.

File	Description
modules/rest-api/partials/user-pw-host-port-params.adoc	Updates the shared parameter definitions for host/port used by REST API curl examples.
modules/rest-api/pages/application-telemetry.adoc	New REST API reference page for application telemetry status and configuration.
modules/manage/pages/monitor/set-up-prometheus-for-monitoring.adoc	Adds a section describing how application telemetry affects Prometheus metrics output.
modules/ROOT/nav.adoc	Adds the new REST API page to the documentation navigation.

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[ingenthr]

Nice work on this @ggray-cb . We're getting a number of questions about this functionality, so it'll be great to see it in the docs.

I had a few small comments and @shivaniguptacb may want to review. Also, it looks like copilot caught a few important things (like the kotlin/python ambiguity).

[shivaniguptasf]

Nice work!
One small thing - I didn't see a mention that in 8.0 it is disabled by default. Might want to add that both to the Server Monitoring page, and to the REST API reference page that you added.

[ggray-cb]

@shivaniguptasf Added default value for the enabled setting, plus added notes stating that it defaults to off but that may change in the future.

[ggray-cb]

Adding @RichardSmedley because he expressed interest in reviewing the current draft. Also added @Peter-Searby in hopes he could review the techical details about what happens if a node hits its limit for connected nodes. @ingenthr asked if there was a way for users to tell this has happened.

[ingenthr]

Nearly there, thanks! There's one bit of ambiguity I think we should try to address if we can. See comments.

[Peter-Searby]

Also added @Peter-Searby in hopes he could review the techical details about what happens if a node hits its limit for connected nodes. @ingenthr asked if there was a way for users to tell this has happened.

That's basically up to the SDKs to handle. When they attempt to connect to a node that is full, they'll try other nodes, but I can't remember the exact details. Users would presumably see this from the SDK logging, but perhaps @DemetrisChr can confirm?

The admins for the cluster would also be able to detect this happening by following the cm_app_telemetry_curr_connections metric. Once this reaches the max scrape clients configured for that node, further connections are rejected.

[Peter-Searby]

I think you misread my comment here. I meant that "state" sounds like a status, not that that is a better way of referring to it. Settings are definitely not a "status" or a "state" in my mind

Reposting comment because I couldn't un-resolve the original comment, so this might have got missed